Charles Laham, M.D., FACC, FRCPC, FSCAI, principal investigator of the IQ-CATEGORIZE Lesions study
June 12, 2014 — Three-dimensional imaging known as 3-D quantitative coronary angiography (3D-QCA) accurately identifies hard-to-see coronary artery lesions that merit further evaluation, according to the IQ-CATEGORIZE Lesions study presented as a late-breaking clinical trial at the Society for Cardiovascular Angiography and Interventions (SCAI) 2014 scientific sessions in Las Vegas.
In patients with symptoms or tests suggestive of coronary artery disease but visibly underwhelming disease on angiography, variation in how the angiogram is interpreted can lead to wide variation in treatment and concerns of over- or under-treatment. This new study evaluates reliability of 3D-QCA as a simple tool to determine lesion severity.
Interventional cardiologists routinely use the caliber of the coronary catheter to determine stent size. In 3D-QCA, a 3-D image is created in a similar way, by using the catheter’s size in two or more angled views to create a proportionate 3-D image.
To evaluate 3D-QCA’s accuracy, researchers reviewed 131 suspicious lesions in 79 patients. They compared average minimum coronary channel (or luminal) diameter (MLD) from two angulated views to the in-lesion percent plaque area stenosis (%PAS), a proven and highly accurate measure taken by intravascular coronary ultrasound (IVUS), which uses an ultrasound catheter probe to view a blockage in cross section.
Prior studies using IVUS have established %PAS >67 percent in left main arteries and >70 percent in non-left main arteries as accurate measures of blockage severity. However, %PAS is less commonly used than other severity measures because it requires additional equipment to be passed down an artery. 3D-QCA has potential advantages, because its 3-D images are constructed using standard coronary angiogram images without need for additional imaging or equipment.
In this study, researchers used a 6 French = 2 mm catheter severity cutoff for small (2.6-3.0 mm) and medium-sized (3.1-4.5 mm) vessels, and an 8 Fr or 2.67 mm cutoff for left main or large (>4.5 mm) vessels. They found average MLD’s less than the cutoffs measured by 3D-QCA were highly predictive of %PAS results. In small and medium vessels, 3D-QCA was highly accurate in predicting severe %PAS >70 percent, which is likely to indicate severe disease (93 percent accuracy in small vessels and 97 percent accuracy in medium vessels). In left main and large vessels, 3D-QCA reliably distinguished severe %PAS >67 percent and >70 percent (94 percent accuracy in left main and 92 percent accuracy in large vessels).
“In symptomatic patients, 3D-QCA using the cutoffs established in this study helps determine the location of relevant severe suspicious blockages that may warrant treatment,” said Charles Laham, M.D., FACC, FRCPC, FSCAI, principal investigator of the study. “3D-QCA appears to be a simple yet reliable tool to help interventional cardiologists distinguish which occult lesions should be further evaluated. The technique can help improve patient care, while reducing variation in care.”
For more information: www.scai.org